(1) Field of the Invention
The present invention relates to a transmission control method for a vehicle, in which shifting between drive ranges in forward and reverse respectively is carried out by engaging and disengaging forward and reverse drive clutches (direction clutches) as well as at least first and second drive clutches (speed clutches), and to a transmission control method especially suitable for use in construction vehicles such as a power shovel, shovel dozer, bulldozer, wheeled loader and truck (including damped motor lorry).
(2) Description of the Related Art
When the drive speed of a vehicle of the above type is changed in the same drive direction or reverse drive direction with a conventional transmission control method, shifting between drive ranges in forward and reverse respectively is accomplished by engagement and disengagement of direction and speed clutches (in this case, these direction clutches are load clutches) in the following manner: Firstly, a speed clutch to be disengaged is disengaged, and either forward direction clutch or reverse direction clutch which is in an engaged state is disengaged. Then, a speed clutch to be engaged is engaged and either the forward direction clutch or reverse direction clutch is engaged.